Thermal-type marker



April 1950 R; BASIAGO 2,934,395

THERMAL-TYPE MARKER Fild July 9, 1957 i207" 2?Z"\'i?d INVENTOR i? Rg nBanjo United States Patent C THERMAL-TYPE MARKER Raymond Basiago, MorrisPlains, N.J., assignor to McGraw-Edison Company, Elgin, 111., acorporation of Delaware Application July 9, 1957, Serial No. 670,810

Claims. (Cl. 346139) This invention relates to thermal devices formarking heat-sensitive paper or other such material, and moreparticularly it relates to improved forms of thermal markers adapted foruse as indexing devices in dictating machnies.

It is a common practice to provide dictating machines with an indexinghead that is moved in correspondence with the traveling movement of thecarriage for making marks on an index slip at points therealongcorresponding to places on the record where the dictator wishes to makelength, correction, rush or other indications in connection with thedictated matter. Such marks usually been made by punching the index slipor by scratching a slip made of specially-treated paper to expose anunderlying film or lamination of a different color. The present markeris of the thermal type having an exposed conductor element which can beelectrically heated to make fine marks on specially-treatedheat-sensitive paper,

An object of my invention is to provide a simplified design of thermalmarker which has long life and low power requirements, and which iseconomical to produce. In particular, an object of my invention in thisrespect is to provide a design which eliminates the expense of fineresistance wire and of complicated procedures in suitably mounting suchwire.

In order to obtain the necessary heating within reasonable power limitsa thin thread-like conductor element as of Nichrome is commonly used. Ifa fine resistance wire of such material is employed, difficultproduction problems are encountered in providing the wire with a firmprotective backing or support while still exposing an edge of the wirefor contact with the heat-sensitive paper, in concentrating the heatingeffect to the exposed portion of the wire, and in making suitable leadwire connections to such fine wire. These problems are accentuatedfurther when the thermal marker is to have several exposed heaterelements which are to be selectively energized for making marks indifferent rows or columns for indicating different indexing functionssuch aslength, correction, rush, etc.

By the present invention these problems are solved economically by asimple design which uses a thin, metal foil as the conductor element.This foil is formed as by "stamping so as to have a narrow heaterstripprovided with integral low-resistance side extensions forming widthof the heater strip is reduced sufiiciently to pro- "ice vide it withthe desired high resistance. Also, by such grinding the exposed surfacesof the several heater elements are made flush with a planar surface ofthe mounting structure for even engagement with a flat surface of amaterial to be marked. Such device comprises only low-cost parts whichcan be fabricated economically to close tolerances into a solid unitarystructure of an efiicient design capable of long periods of use withoutmechanical or electrical failure.

These and other objects and features of my invention will be apparentfrom the following description and the appended claims.

In the description of my invention reference is had to the accompanyingdrawings, of which:

Figure 1 is a side view of a marking device of my invention and of acarriage therefor, showing the marking device in operative engagementwith an index slip of a dictating machine, the mounting for the indexslip and for the carriage being shown in cross section;

Figure 2 is a plan view of the apparatus in Figure 1;

Figure 3 is a side elevation of a first subassembly used in producingthe marking device of my invention;

Figure 4 is a plan view showing a subassembly of the device in a secondstage of completion;

Figure 5 is a side elevational view of the subassembly of Figure 4;

Figure 6 is a fractional cross sectional view to enlarged scale showingthe marking device as it appears on the line 66 of Figure 7;

Figure 7 is a cross sectional view taken on the line 7-7 of Figure 6;

Figure 8 is an elevational end View of a marking device; and

Figure 9 is a schematic diagram of a control circuit for the presentmarking device.

The present marking device 10 is provided preferably in a block shapehaving a planar bottom face 11 provided with one or more heater elements12 (three being shown by Way of example and referred to respectively as12a, 12b and Me) which are flush with the bottom face and disposed in acentral plane lengthwise of the device. The housing 13 is preferablymade of a suitable plastic such as Lucite having holes 14 in itsopposite side walls (Figure 8) for receiving trunnions 15 of a U- shapedmounting spring 16. The back end portion of this spring is mounted flaton the top side of a carriage 17 and secured thereto by a clamping screw18. The carriage is, for example, in the form of a plate havingapertured lugs 19 turned down at its sides through which is fitted asleeve bearing 20. The bearing is mounted slidably on a support rod 21fractionally shown. A rear portion of the carriage rests on a secondcross rod 22 parallel with the first rod 21, and is retained slidablythereon by two lugs 23 struck downwardly from the side portions of thecarriage at a sufiicient distance for engagement with the underside ofthe rod 22. Under influence of the mounting spring 16 the marking unitis pressed downwardly fiat against an index slip 24 of a heat-sensitivepaper supported in a holder 25 having the opposite edges 25a folded overto overlap the opposite edges of the slip and retain the slip in place.The slip has three tracks lengthwise thereof referred to respectively as26a, 26b and 260, which are adapted for receiving marks from therespective heater elements 12a, 12b and to indicate respectively length,correction and rush. Such marks are short colored lines as indicated,for example, at 27a, 27b and 270 in Figure 2. The heat-sensitive papermay be of any commercial form such, for example, as that supplied by theMinnestoa Mining 8; Manufacturing Company of St. Paul, Minnesota. Thisis a white paper which turns to a dark color at any point where it issuitably heated.

The heater elements 12 are formed from a rectangular piece 28 of metalfoil having initially an excess height as shown in Figure 3. This foilis made preferably of Nichrome and has about .002 thickness. The foil iscut out as by stamping and in the same opera,- tion is provided withthree triangular holes 29a, 29b and 29c along the bottom edge thereof.The portions of the foil below these triangular openings form the heaterstrips 12a, 12b and 12c aforementioned. Placed fiat against the oppositesides of the lower apertured portion of the foil to a height of nearlythe apices of the triangular holes 29 are side plates 30 of insulatingmaterial such as of Micarta. These plates may be typically about .015"in thickness. The inside surfaces of these insulator plates are securedto the foil and to each other through the holes 29 by means of asuitable thermoplastic cement such as Ciba Araldite No. 502. Thiscementing is done by coating the adjoining surfaces, clamping the platestogether against the foil, heating the assembly to about 100 C. for tento thirty minutes, and then allowing the same to cool to roomtemperature. After the laminated structure is so formed the upper excessportion of the foil 28 is cut off at the line 31 in Figure 3 through theapices of the triangular holes 29a, 29b and 290 so as to form successiveterminals 32a, 32b, 32c and 32d extending from a side of the laminatedfoil plate structure. The upper tabs of these terminals which extendabove the side plates 30 are then folded over against the top end faceof one of these plates and respective lead wires 33a, 33b, 33c and 33dare soldered thereto as indicated in Figure 4. These lead wires have asuitable insulative covering such as of Formvar, and are bunchedtogether and lead from the subassembly unit 28-36 along the top edgethereof. Next, the bottom face of the subassembly unit is ground downuntil the width of the heater strip elements 12 is reduced to thedesired dimension to cause the heater elements between the successiveterminals 32 to have the desired high resistance. As a final operation,this subassembly unit is mounted in the housing 13 with the bottom facethereof projecting slightly below the housing and with the lead wires 33running out one end thereof. Such housing may be, for example, a blockof suitable plastic molded with a central slot 34 running out one endthereof to receive the subassembly unit, and the unit may be secured inplace by cementing as with Duco cement. Preferably, the block 13 is madeof clear plastic and the cement for holding the unit in place is coloredblack as by India ink, so that the finished unit has the appearance of aclear plastic block with a fine coloredline running lengthwise thereofto indicate the place of the heater elements. As before described, thehousing has side holes 14 receiving the end trunnions of the mountingspring 16.

A control circuit for the marker is illustrated in Figure 9. Thiscircuit is connected through a transformer 35 to a source of powerdesignated by the terminals 36. In the control circuit there is arectifier 37, load resistor 33 and condenser 39. The power for heatingthe thermal marker elements 12 is derived by discharging the condenser39 through the circuit 40. The circuit 46 is connectable selectivelyacross the respective heater elements 12a, 12b and 120 via respectivepushbutton switches indicated at 41a, 41b and 410. For example, when oneof these switches is depressed the circuit is closed across thecondenser 39 through the respective heater element to cause thecondenser to be discharged through that element. This causes the heaterelement to be heated momentarily sufiiciently to make a suitable mark onthe associated heat-sensitive index slip 24, the time of the heatingbeing established by the time constant of the condenser 39 andresistance in the discharge circuit. It is found that about .27 wattsecond of power is ample for momentarily heating the respective heaterelements and that such amount of heating power is obtained when thecondenser 39 has about 390 mf. and is charged to about 30 volts.Although the operator may continue to hold one or another of the controlswitches 43 closed for a substantial length of time, it is only theinitial discharge from the condenser 39 that is effective in heating theselected marker element because the load resistor 33 is suflicientlyhigh to prevent a continued heating of that element to an operativetemperature. However, the load resistor 38 will allow the condenser tobe quickly recharged for a successive marking operation as soon as thecontrol switch is released.

The particular embodiment of my invention herein shown and described isintended to be illustrative and not limitative of my invention since thesame is subject to changes and modifications without departure from thescope of my invention, which I endeavor to express according to thefollowing claims.

I claim:

1. A thermal-type marker for operation on a heatsensitive materialcomprising an elongated laminated structure including two insulatingplates and an intervening metal foil, said foil comp-rising a narrow,elongated heater strip extending lengthwise of said laminated structureand provided with a plurality of integral side extensions at rightangles to the lengthwise dimensions of said heater strip formingelectrical terminals extending beyond one side of said laminatedstructure, said terminals having dimensions in the direction along saidstrip substantially greater than the width of said strip, said laminatedstructure having a side face with an exposed edge of said strip portionof the foil flush therewith for contact with said heat-sensitivematerial, and lead wires connected to said terminals for conductingcurrent to said strip portion to heat the same.

2. A selectively-energizable thermal-type indexing marker for marking ona heat sensitive material in respective tracks thereon, comprising anelongated laminated structure of two insulating plates and anintervening metal foil, said foil comprising a narrow elongated heaterstrip lengthwise of said laminated structure and provided with integralside extensions at right angles to the lengthwise dimension of saidheater strip and at intervals therealong forming electrical terminals,said terminals extending beyond one side of said laminated structure andhaving a width dimension along said heater strip substantially greaterthan the width of said strip, said laminated structure having a sideface exposing an edge of said strip of said foil for contact with saidheatsensitive material, and lead wires connected to said terminals forconducting current to said respective strip port10ns of the foil.

3. The thermal-type marker set forth in claim 1 wherein said terminalshave an increasing width proceeding from said heater strip.

4. A thermal-type indexing marker adapted for selectively marking inrows on a heat-sensitive paper, comprising a body of insulating materialhaving a side face for engaging said paper and having a one piecemetalfoil embedded in said body at right angles to said side face with anedge of the foil substantially flush with said side face, said foilcomprising a single narrow heater strip at said side face havingintegral side extensions at right angles to the lengthwise dimension ofsaid heater strip and at intervals therealong forming electricalterminals, said terminals having width dimensions along the heater stripgreater than the width of the strip itself leading out of another faceof said body, and lead wires connected to said terminals respectivelyfor conducting current to heat selectively the heater strip portions ofsaid foil between successive terminals.

5. The indexing marker set forth in claim 4 wherein said terminals havea width dimension along said heater strip which increases proceedingfrom said heater strip and the average width of each of said terminalsis substantially greater than the width of said heater strip whereby toconfine largely the heating efiect of an electrical current to theheater strip.

References Cited in the file of this patent UNITED STATES PATENTS GlynnSept. 26, Cox June 17, Holden et al. May 18, Greig July 6, Boyan Ian. 8,

FOREIGN PATENTS Great Britain May 11,

